Table Of Contents

Learn Failures from History RAM

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Last Modified: November 23, 2020

Use Learn Failures from History RAM to automatically edit the pin states of a pattern to change failing pin states to ones that will pass.

To execute this command, use the toolbar button on the pattern document while viewing History RAM failures in the Grid view of the document with the History RAM Overlay feature enabled. Ensure that there is at least one failure to learn. Before beginning to edit a pattern, the Digital Pattern Editor displays a dialog box with the options described below.

Once you confirm your options, the DPE will edit the pin states for the failures currently in History RAM. If your pattern has more failures than will fit in History RAM, burst the pattern again after confirming your options and execute the command again to learn additional failures.

Configuring Learn Failures from History RAM

The Learn Failures from History RAM dialog box includes the following options:

  • Which Pin States — Specifies the pin states from which to learn failures.
    • All Failures in History RAM — Specifies to learn failures from all failed pin states in History RAM.
    • Selected Failures — Specifies to learn failures from selected failed pin states in History RAM.
  • Replace With — Specifies what to replace the specified failures with.
    • Actual from History RAM — Replaces the specified failures with the pin states that match the actual measured results from History RAM.
    • X — Replaces the specified failures with the X pin state.
  • On Conflict — Specifies how to replace specified failures when there is a conflict. The DPE considers a failure to be a conflict in the following circumstances:
    • The existing pin state is a - or E.
    • There is more than one result for the failure in History RAM and at least one of those results conflicts with the other results
    • At least one actual measured result for the failure in History RAM is both high and low. This can happen when the VOH and VOL levels are inverted, or with a compare strobe located at a fast rising or falling edge.
    • The actual measured result in History RAM is an M and the failure is on a scan output pin in a scan vector. Scan output pins only support the L, H, and X pin states.
    • The failure is on a parallel pin in a scan vector.
    • Stop — Specifies to stop learning failures at the first conflict. The DPE selects the failure with the conflict and scrolls it into view.
    • Replace With X — Specifies to replace the conflicting failures with the X pin state.
    • Skip Conflicting — Specifies to skip over any conflicting failures.
  • Add Vector Comment — Specifies a comment to append to each vector in which the DPE modifies a pin state for the Learn Failures from History RAM operation. This field does not accept the <Enter> or <Tab> keys.

    For scan vectors, comments can only be added to the template rows of the vector, so the DPE also appends the ranges of scan indices in which a pin state was learned. For example, if a pin state was learned on scan cycles 0, 1, 2, and 4, the default comment appended would be: Learned (scan indices: 0-2, 4). If the vector already has an existing comment, the DPE will append the comment you specify using a comma as a delimiter to separate it from the existing comment. If you leave this setting blank, the DPE does not append any comments for this operation.


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